Alka seltzer rockets are a popular experiment used to demonstrate pressure build up to younger children. We decided to further this common experiment to explore how pressure build up differentiates when the amounts of the reactants (Alka seltzer and water) are changed within set boundaries. We set grams of alka seltzer as the independent variable in one trial and then milliliters of water as the independent variable in the other trial.
Our experiment was based off the chemical reaction that takes place when an alka seltzer tablet is dropped in water in an airtight container. While this also creates a physical change, the alka seltzer tablets dissolving into the water, we focused on the chemical reaction. When the tablet is placed in the water and begins to dissolve, an acid base reaction between the citric acid and sodium bicarbonate takes place and creates carbon dioxide gas.
The formula for this is: NaHCO3 + Citric acid ---> CO2 + H2O + Sodium Citrate The carbon dioxide gas builds pressure in the container and propels the rocket to shoot upwards. The purpose of our experiment was to find the most time efficient mix of water and alka seltzer, that would result in the shortest launch time and longest flight time.
Procedure
To conduct this experiment we used very basic equipment. One film canister, two timers, some water, and some generic, effervescent, Alka Seltzer. First we filled the film canister with 9.5 mL of water, (about a quarter of the way full) and then added 3.18 g of Alka seltzer (one tablet). Once the water and the Alka Sletzer were in the film canister, we quickly shut the lid and placed the canister on the ground, top facing downwards. As soon as one of us shut the lid (which is when the pressure starts to build up) we called for the other to start the first timer. When the rocket took off, we stopped the first timer (which saved the launch time) and simultaneously started the second timer. We stopped the second timer when the rocket hit the ground again. We repeated this procedure three times with 9.5 mL of water and then took the average of the three launch and flight times and graphed it. We then kept the water at a constant of 9.5 mL and repeated the experiment four more times changing the amount of Alka Seltzer to 6.36g (two tablets), 9.54 g (three tablets), 12.72 g (four tablets), and 1.59 g (one half of a tablet) completing three sub-trials and finding the average launch and flight times each time . We then changed the amount to 3.18 g (one tablet) of Alka Seltzer and ran five trials changing the amount of water to 9.5 mL, 19 mL, 25 mL, 4.75 mL, and 14.25 mL and repeated the whole experiment again with three sub-trials for every changing amount of water.
Here is a video showing what a trial consisted of:
Results
Changing Alka Seltzer Amounts
Above are the graphed results for the five trials in which the constant was 9.5 mL of water. The X-axis represents the changed amount of Alka Seltzer (in grams) for each of the five trials. The Y-axis represents time in seconds. The results for launch are shown in blue and the results for flight are shown in red.
Changing Water Amounts
Above are the graphed results for the five trials in which the constant was 3.18 grams of Alka Seltzer. The X-axis represents the changed amount of water (in mL) for each of the five trials. The Y-axis represents time in seconds. The results for launch are shown in blue and the results for flight are shown in red.
Conclusions
From these results we can conclude that trial 5 of our changing tablet amount segment is the best because it presents the best balance of short launch time and long flight time. Over all the type of mixture that is the best consists of less water, 9.5 mL or about ¼ of the way full in the film canister, and more Alka Seltzer, approximately 4 tablets or 12.72 grams of alka seltzer, because it allows a lot of pressure to build up (resulting in a long flight) and leaves a medium amount of room for it to build up (allowing for fairly short launch time.) Some errors that probably occurred were in the timer operation. Due to human reaction time we probably did not always start or stop the timer at exactly the right moment. Another error is that from trial to trial, the time it took to close the lid and begin the pressure build up probably varied, meaning that varying amounts of gas escaped the canister on each trial. Throughout the course of this experiment we noticed that while launch time varied greatly from trial to trial, flight time did not vary as much. Why that is may be a good question to explore further with this experiment. A way to improve this experiment might be to conduct it in a more controlled environment where the results can't be altered by wind, humidity, temperature, or any other elements.
References
Chen, Y-H, and Yaung, J-F. “Alka Seltzer Fizzing- Determination of Percent by Mass of NaHCO3 in Alka Seltzer Tablets.” J. Chem. Ed. vol 79, no.7, July 2002. p. 848
Table of Contents
Alka Seltzer Rockets
Lizzie, Lauren
Introduction
Alka seltzer rockets are a popular experiment used to demonstrate pressure build up to younger children. We decided to further this common experiment to explore how pressure build up differentiates when the amounts of the reactants (Alka seltzer and water) are changed within set boundaries. We set grams of alka seltzer as the independent variable in one trial and then milliliters of water as the independent variable in the other trial.
Our experiment was based off the chemical reaction that takes place when an alka seltzer tablet is dropped in water in an airtight container. While this also creates a physical change, the alka seltzer tablets dissolving into the water, we focused on the chemical reaction. When the tablet is placed in the water and begins to dissolve, an acid base reaction between the citric acid and sodium bicarbonate takes place and creates carbon dioxide gas.
The formula for this is:
NaHCO3 + Citric acid ---> CO2 + H2O + Sodium Citrate
The carbon dioxide gas builds pressure in the container and propels the rocket to shoot upwards. The purpose of our experiment was to find the most time efficient mix of water and alka seltzer, that would result in the shortest launch time and longest flight time.
Procedure
To conduct this experiment we used very basic equipment. One film canister, two timers, some water, and some generic, effervescent, Alka Seltzer. First we filled the film canister with 9.5 mL of water, (about a quarter of the way full) and then added 3.18 g of Alka seltzer (one tablet). Once the water and the Alka Sletzer were in the film canister, we quickly shut the lid and placed the canister on the ground, top facing downwards. As soon as one of us shut the lid (which is when the pressure starts to build up) we called for the other to start the first timer. When the rocket took off, we stopped the first timer (which saved the launch time) and simultaneously started the second timer. We stopped the second timer when the rocket hit the ground again. We repeated this procedure three times with 9.5 mL of water and then took the average of the three launch and flight times and graphed it. We then kept the water at a constant of 9.5 mL and repeated the experiment four more times changing the amount of Alka Seltzer to 6.36g (two tablets), 9.54 g (three tablets), 12.72 g (four tablets), and 1.59 g (one half of a tablet) completing three sub-trials and finding the average launch and flight times each time . We then changed the amount to 3.18 g (one tablet) of Alka Seltzer and ran five trials changing the amount of water to 9.5 mL, 19 mL, 25 mL, 4.75 mL, and 14.25 mL and repeated the whole experiment again with three sub-trials for every changing amount of water.Here is a video showing what a trial consisted of:
Results
Above are the graphed results for the five trials in which the constant was 9.5 mL of water. The X-axis represents the changed amount of Alka Seltzer (in grams) for each of the five trials. The Y-axis represents time in seconds. The results for launch are shown in blue and the results for flight are shown in red.
Above are the graphed results for the five trials in which the constant was 3.18 grams of Alka Seltzer. The X-axis represents the changed amount of water (in mL) for each of the five trials. The Y-axis represents time in seconds. The results for launch are shown in blue and the results for flight are shown in red.
Conclusions
From these results we can conclude that trial 5 of our changing tablet amount segment is the best because it presents the best balance of short launch time and long flight time. Over all the type of mixture that is the best consists of less water, 9.5 mL or about ¼ of the way full in the film canister, and more Alka Seltzer, approximately 4 tablets or 12.72 grams of alka seltzer, because it allows a lot of pressure to build up (resulting in a long flight) and leaves a medium amount of room for it to build up (allowing for fairly short launch time.) Some errors that probably occurred were in the timer operation. Due to human reaction time we probably did not always start or stop the timer at exactly the right moment. Another error is that from trial to trial, the time it took to close the lid and begin the pressure build up probably varied, meaning that varying amounts of gas escaped the canister on each trial. Throughout the course of this experiment we noticed that while launch time varied greatly from trial to trial, flight time did not vary as much. Why that is may be a good question to explore further with this experiment. A way to improve this experiment might be to conduct it in a more controlled environment where the results can't be altered by wind, humidity, temperature, or any other elements.References
Chen, Y-H, and Yaung, J-F. “Alka Seltzer Fizzing- Determination of Percent by Mass of NaHCO3 in Alka Seltzer Tablets.” J. Chem. Ed. vol 79, no.7, July 2002. p. 848
Ophardt, Charles E. Chemical Properties. 2003. 26 January, 2010.